Reversible polarity generator



Dec. 6, 1949 H. s. JACOBS ET AL 2,490,629

REVERSIBLE FOLARITY GENERATOR Filed March 13, 1948 3 Sheets-Sheet 1 & QI

Dec. 6, 1949 H. s. JACOBS ETAL 2,490,629

REVERSIBLE POLARITY GENERATOR Filed larch 1:, 1948 s Sheets-Sheet 2 Dec.'6, 1949 H. s. JACOBS ET AL REVERS IBLE POLARITY GENERATOR 3Sheets-Sheet 3 Filed March 15, 1948 Patented n... s, 1949 2,490,829REVERSIBLE POLARITY GENERATOR Henry S. Jacobs waukee, Wis.,

Wisconsin and William J. Cherones, Milassiguors to Harnischfegerporation, Milwaukee,

Wis., a corporation of Application March 13, 1948, Serial No. 14,688

8 Claims.

This invention relates to reversible polarity direct current generatorsof the type commonly employed for electro-mechanical power transmittersin which a motor of the separately excited type is directly connected tothe terminals of the generator so that speed and direction of rotationof the motor may be controlled by regulation of comparatively moderatefield currents of the generator. More specifically, the inventionresides in an improved generator of the type above mentioned in whichseparate forward and reverse field windings are employed, each-of saidwindings being arranged for independent excitation by independentadjustable excitation current sources and each of said windings alsobeing arranged for supplementary self-excitation derived from thegenerator armature through blocking rectifier means which discriminateon the basis of polarity of generator output in such manner as tosupplement the excitation only of that winding which is being excited bysaid independent excitation sources, such supplementary excitationcurrent being so limited as to amount that the same is insufficient tomaintain magnetization of the generator field in the absence of saidindependent excitation whereby the polarity and output of the generatorremains at all times subject to the command of the adjustableindependent excitation sources.

One object of this invention is to provide an improved generator of thetype above defined in which field windings active at any one time aremore simple in design and construction and, for a given capacity, ofreduced self-inductance so as to provide a generator which responds morerapidly to sudden variations of load.

Another object is to provide a generator of the character described inwhich the field currents required to be regulated in order to regulatethe output of the generator are moderate in amount and capable of beingregulated by simple and reliable apparatus which if desired may be soconstructed as to be free of dependence upon switches or other movablecontacts.

Another object of this invention is to provide a generator of thecharacter described wherein smoother and more rapid acceleration of aload energized thereby may be obtained with diminished commutatingdifiiculties.

Another object is to provide a generator of the character describedwhich will operate with reduced electrical and mechanical shock toitself and a load driven thereby both during rapid alteration of loadand during plugging reversal.

The above and other objects and advantages of this invention will becomeapparent from the description which follows. This invention is hereindescribed by reference to the accompanying drawings, forming a parthereof, in which there is set forth by way of illustration and not oflimitation, specific forms in which apparatus may be constructed inaccordance therewith.

In the drawings:

Fig. l is a front view in elevation with parts broken away or a variableimpedance controller of a type which may be used in conjunction withthis invention.

Fig. 2 is a side view-in section of the controller i5showninFig.l;

Fig. 3 is a front view in elevation of the controller shown in Fig. lwith the cover removed and certain parts broken away;

Fig. 4 is a detail top plan view in section viewed through the plane Hindicated in Fig. 3;

Fig. 5 is a diagrammatic showing of a circuit showing the controllerdepicted in Fig. 1 employed for regulating two separate generators orloads;

Fig. 6 is a diagrammatic showing of one form of the circuit of thisinvention employing a controller of the type shown in Fig. l to controla generator, and

Fig.7 is a showing of another form of the circuit of this inventionemploying an adJustable rheostat for controlling a generator.

As appears in Fig. 6 of the drawinss, an apparatus in accordance withthis invention may be constructed by providing a generator designatedgenerally by the numeral i having a field frame 2 in which a pluralityof pole pieces I are mounted. Arranged for rotation within the fieldframe 2 is an armature I having a commutator 5 engaged by brushes 8.Armature current is carried from the brushes 6 on one hand through lead1 to terminal I and on the other hand through series field windings landII and lead ii to terminal II. The armature Q is arranged to be drivenby any suitable outside source of mechanical power.

Also mounted upon the pole pieces I are forward field windings l3 andI4. The windings l3 and H are designated forward field windings in orderto signify that excitation thereof results in the appearance at thegenerator terminals I and I! of an output of such polarity as to cause amotor I! connected thereto to rotate in a forward direction. Motor II isprovided with a separately excited field I. so that the direction ofrotation of said motor is determined by the polarity of currentfurnished through terminals put at the generator terminal of such tocause reverse rotation 01 motor 15.

For thepurpose of supplying a part of the excitation current lor theiorward field windings l2 and It a source or supply of alternatingcurrent comprismg supply leads l9 and is provided. Connected with lead20 by means of lead 2| is a winding 22 of an impedance controller 23which will be described in greater detail hereinarter. Extending n'omwinding 22 is a lead 24 which joins with one input terminal of afullwave dry-disc rectifier 25. The other input terminal or rectiner 25is connected by means 01 lead 26 with supply lead ID as shown.

One output terminal or the rectifier 25 is connected by means or lead 21with winding l3 which 28 with winding l4 which in turn is connected bylead 29 with the other The rectifie output or rectiner 25 is thus causedto flow in In a more iully described hereinafter impedance controller 23may be adjusted to supply alternating current to the rectifier 25 inamounts ranging from approximately zero up to a predetermined maximum.

In manner similar to that described above the input terminals ofrectifier 30 are connected by One output terminal of rectifier 30 isconnected through lead to winding I 8 which is joined in turn throughlead 36 with winding For the purpose of supplementing excitation ofwindings l3 rectifier 2!, terminal nected through lead 4| and blockingrectifier 42 with lead 27.

current begins to pass rectifier 42 supplementing the excitation ofwindings l3 and I4.

As the to rise plates 61 citation source on the one hand and thegenerator other hand.

be desirable that the output of generator I and hence control over themotor l5 be completely-at the command of the controller 23. To accom- Insimilar manner output of generator I is arranged to supply supplementaryexcitation to the reverse windings I! and I8. This is accomplished bythe circuit formed by lead 45 which joins with The furnishing of thisself-excitation circuit for windings I I and I8 is comparable in allrespects with that which supplies supplementary excitation to windingsl3 and I4 as described above.

To improve the wave form of current supplied to rectifier 25, acondenser 50 is connected as shown between leads 24 troller shown inthe; drawings a laminated stator ring 54 is mounted between clampingrings 5555 and held on a supporting base 56. Secured to rear bellhousing 51 having a shaft supporting bearing 58 at its supportingbearing 60.

Integrally formed with the stator ring 54 are inwardly extending polepieces 6|, 62, 63 and 64, the same terminating on the surface of animagi- Mounted upon pole piece 62 is In similar fashion winding 32 abovedescribed is mounted as shown upon pole piece 6|. Pole pieces 63 and 64carry windings 22a and 32a which may be employed, if desired,v forsimultaneous action similar to that of windings 22 and 32, or may beconnected in made up clamped between end and 68 by means of bolts 69 and70.

upon shaft 65, is a laminated rotor 66 of laminations as shown,

14 interpoles may QAOOJSO Bolts 88 and 18 are insulated from the endplates 81 and 88 by means of bushings H to currents which mightotherwise result due to transformer action.

The laminated rotor 88 is cut away on opposite sides with semi-circularconcavities 12 as appears more clearly in Fig. 5. The laminated rotor 88is also cut away as shown in Fig. 4 to form the bevelled faces 18adjacent the cusps formed by the concavities 12. In this way thecylindrical outer surfaceoi the rotor 88 is divided into 2 hexagonalfaces one of which reaches to a point beneath pole piece 8| and theother of which reaches to a point beneath pole piece 82.

The shaft 88 extends outwardly from the front bell housing 58 where itis engaged by an operating handle 14. Secured to the operating handle 14is a detent sector 18 having a notch positioned to be engaged by springpressed ball 18 when the controller handle 14 is in mid position.

In addition to the pole pieces ii to 84, inclusive, a more completereturn flux path may be provided, if desired, by means of pole pieces11--11, but their presence is not essential to the operation of theapparatus. Also, to reduce the effort required to move the controllerhandle be inserted between the windings 82 and 22 and between thewindings 82a and 22a and provided with interpole windings which arecontinuously excited.

In operation, with the controller in the position shown in the drawingsa fiux path is provided in the case of winding 22 through the pole piece6|, the rotor 88, the supplementary pole 11 and the field ring 84. Byreason of this magnetic circuit, the impedance of winding 32 is high andwhen contained in a circuit as shown in Fig. 6 will pass little currenton this account. The same is true of winding 22. Upon movement of thecontroller handle 14 in a clockwise direction rotor 86 begins to movefrom beneath the end of pole piece BI and to more completely occupy thearea beneath the pole piece 62. As this motion takes place the impedanceof winding 32 diminishes while that of winding 22 is maintained or evento some small extent increased. When the controller handle 14 is movedin a counter-clockwise direction the opposite eflect occurs and theimpedance of winding 22 diminishes while that of winding 82 ismaintained. By reason of the regulating action thus produced control ofgenerator I is accomplished without resort to any switches or anymovable contacts. Where heavy duty electro-mechanical drives areemployed, a control system which is free of the maintenance difficultiesusually attendant upon switching or sliding contact apparatus is thusavoided.

As explained above, windings 32a and 22a may be employed to supplementthe effect of windings 12 and 22 or as appears in Fig. they may beemployed to simultaneously regulate the output of separate generators.In the case of generators of larger size or of a type employing morethan 2 pole pieces the field windings may be subdivided and separatelyhandled as separate loads as indicated by load A and load B in Fig. 5.

The generator of this invention may also be constructed when of lowercapacity and smaller size so as to be operated by the simplified circuitappearing in Fig. 7. In Fig. I a generator 18 is shown provided with aforward field winding 18 and a separate reverse field winding 88. Fieldwinding 18 is connected by lead 8I and lead 82 with a variableresistance element 88.

'A movable contact 84 arranged to engage the element 88 is connected inturn to a separate direct current excitation source 88. The source 88 isJoined on the other hand by leads 88 and 81 with the windin 18.

The forward field winding 18 is also connected through lead 8I, lead 88,resistor 88 and lead 88 with terminal 8| of generator 18. The oppositeterminal 82 of generator 18 is connected through lead 83, lead 84,blocking rectifier 95, lead 88 and lead 81 to the opposite side offorward fiel d winding 18. Thus upon movement of contact 84 intoengagement with resistance element 88, forward field winding 18 becomesfirst independently excited from a source 85, and then bothindependently and self-excited as the output of generator 18 builds up.Movement of contact 84 to the mid position or oil position due to theaction of resistance 88 causes the-generator 18 to drop its load. Thepolarity of the output of generator 18 may be reversed in like fashionthrough the action of reverse leld winding 88 which is connected by lead81 and lead 88 with resistance element 98 which may be connected in turnwith the source 85 by movement of contact 84. The source 85 is connectedon the other hand through lead I88 and lead I8I with the opposite sideof reverse field winding 88. Supplementary excitation of reverse fieldwinding 88 is provided through lead I82 which connects through lead 88with terminal iii of generator 18 and joins with field winding 88through blocking rectifier I82, lead I84 and lead IN. The oppositeterminal 82 of generator 18 is joined through lead 83, resistanceelement I85, lead I88 and lead 81 with the opposite side of reversefield 88.

The behavior of the circuit shown in Fig. I is comparable with that ofthe circuit illustrated in Fig, 6 except that operation depends upon themovable contact 84.

In a generator constructed in accordance with this invention each fieldwinding performs the functions of both a self-excited field winding anda separately excited field winding. Because of this dual function theeffective overall field turns and self-inductance of the generator isless than in the ease of a generator of equivalent capacity in whichseparate, self -excited and independently excited windings are employed.The field structure of the generator of this invention, therefore, willrespond more rapidly .to sudden variations of load. With this improvedresponse of the generator field, the intensity and extent of suddensurges of armature current, due to sudden load changes, is substantiallyreduced. This materially improves commutation and reduces mechanicalshock during transient conditions.

As compared with a generator having a single field winding the generatorof this invention will operate with a higher maximum voltage, willproduce a smoother acceleration of the motor driven thereby and onplugging reversal will respond. with substantially less interchangecurrent between the motor and generator. On this account lesscommutation difiiculty, less mechanical shock and less heating of themotor and the generator will occur on plugging.

The presence in the field circuits of the gen erator of this inventionof the rectifiers which are employed, provides a low resistancedischarge path for the field windings when the controller is broughtsuddenly to the off position. Where such discharge is aggravated aswould occur if the generator field were disconnected for any terminalsand reason when the controller is in the full on position the resistors52 and I! will act as an emergency protective device.

We claim:

1. The' combination with a direct current generator having a fieldframe, an armature including a commutator mounted for rotation in saidfield frame, brushes said commutator, and terminals brushes; of aforward field mounted in said field frame; a reverse field windingseparate cuit including a blocking rectifier.

2. The combination with a direct current generator having a field frame,an armature insaid reverse field winding to. cause a reverse outputpolarity opposite to that of to appear at said generator ls; connectionsforming a circuit between said enerator said forward field winding, saidindependent excitation source; and connections forming a circuit betweensaid generator tersaid ciriaid independent excitation source, 1180including current limiting means adapted said armature 3. Thecombination with a direct current genminals 8 erator having a fieldframe, a series field winding in said field frame, an armature includinga commutator mounted for rotation brushes engaging said commu ator, andterseries field winding; and connections forming a circuit between saidgeneratogt erminals and said reverse field winding,

alternating current, a reverse adjustable impedance means in circuitwith said rectifier adapted to adjust the fiow of alternating currentthereto, and circuit connections joining the output of said rectifier tosaid reverse field winding for establishing a field current therein ofsuch polarity as to cause a reverse output of predetermined polarityopposite to that of said forward output to appear at said generatorterminals; connections forming a circuit between said generatorterminals and said forward field winding said circuit including blockingrectifier means disposed to pass current only when of like polarity tothat supplied to said forward field winding by said independentexcitation source, said circuit also including current limiting meansadapted to limit field excitation supplied by said armature to saidforward field winding to a value insufficient to maintain magnetizationof said field in the absence of excitation supplied by said independentexcitation source; and con-- nections forming a circuit between saidgenerator terminals and said reverse field winding, said circuitincluding blocking rectifier means disposed to pass current only when oflike polarity to that supplied to said reverse field winding by saidindependent excitation source, said circuit also including currentlimiting means adapted to limit field excitation supplied by saidarmature to said reverse field winding to a value insufficient tomaintain magnetization of said field in the absence of excitationsupplied by said independent excitation source.

5. The combination with a direct current generator having a field frame,an armature including a commutator mounted for rotation in said fieldframe, brushes engaging said commutator, and terminals connected to saidbrushes; of a forward field winding mounted in said field frame; areverse field winding separate from said forward field winding mountedin said field frame; an independent source of excitation current forsaid forward field winding comprising a rectifier adapted to beconnected to a source of alternating current, a forward adjustableimpedance means in circuit with said rectifier adapted to adjust thefiow of alternating current thereto, and circuit connections joining theoutl0 plied to said forward field winding bysaid independent excitationsource, said circuit also including current limiting adapted to limitfield excitation supplied by said armature to said forward field windingto a value insufficient to maintain ma netization of said field in theabsence of excitation supplied by said independent excitation source;and connections forming a circuit between said generator terminals andsaid reverse field windin said circuit including unidirectionallyconducting means disposed to pass current only when or like polarity tothat supplied to said reverse field winding by said independentexcitation source, said circuit also including current limitingresistance means adapted to limit-field excitation supplied by saidarmature to said reverse field winding to a value insumcient to maintainma netization of said field in the absence of excitation supplied bysaid independent excitation source.

6. The combination with a direct current generator having a field frame,an armature including a commutator mounted for rotation in said fieldframe, brushes enga ing said commutator, and terminals connected to saidbrushes; of a forward field winding mounted in said field frame; areverse field winding separate from said forward field winding mountedin said field frame; an impedance controller having a forward impedancewinding, a reverse impedance winding, a magnetic frame, and anadjustably movable magnetic member adapted to be moved to selectivelydiminish the impedances of said forward and reverse impedance windin s;means including a rectifier in circuit with said forward impedancewinding adapted to be connected to put of said rectifier to said forwardfield winding for establishing a field current therein of such polarityas to cause a forward output of predetermined polarity to appear at saidgenerator v terminals; an independent source of excitation current forsaid reverse field winding comprising a rectifier adapted to beconnected to a source of alternating current, a reverse adjustableimpedance means in circuit with said rectifier adapted to adjust theflow of alternating current thereto, and circuit connections joining theoutput of said rectifier to said reverse field winding for establishinga field current therein of such polarity as to cause a reverse output ofpredetermined polarity opposite to that of said forward output to appearat said generator terminals; interlocking means cooperatively engagingsaid forward and reverse adjustable impedance means adapted to correlateadjustment thereof to cause the impedance of either of the same to be ata maximum whenever the impedance of the other is adjusted to a valueless than maximum, connections forming a circuit between said generatorterminals and said forward field winding said circuit includingunidirectionally conducting means disposed to pass current only when oflike polarity to that supa source of alternating current and connectedto said forward field windin to supply independent direct excitationcurrent thereto in amount determined by the position of adjustment ofsaid impedance controller for establishing a field current in saidforward field winding of such polarity as to cause a forward output ofpredetermined polarity to appear at said generator terminals; meansincluding a second rectifier in circuit with said reverse impedancewinding adapted to be connected to a source of alternating current andconnected to said reverse field winding to supply independent directexcitation current thereto in amount determined by the position ofadjustment of said impedance controller for establishing a field currentin said reverse field winding of such polarity as to cause a reverseoutput of predetermined polarity opposite to that of said forward outputto appear at said generator terminals; connections forming a circuitbetween said generator terminals and said forward field winding saidcircuit including unidirectionaliy conducting means disposed to passcurrent only when of like polarity to that supplied to said forwardfield winding by said inde endent excitation source, said ci cuit alsoincludin current limiting resistance means adapted to limit fieldexcitation supplied by said armature to said forward field winding to avalue insufficient to maintain magnetization of said field in theabsence of excitation supplied by said independent excitation source;and connections forming a circuit between said generator terminals andsaid reverse field winding, said circuit including unidirectionallyconducting means disposed to pass current only when of like polarity tothat supplied to said reverse field winding by said independentexcitation source, said circuit also including current limitingresistance means resistance means i 11 12 adapted to limit fieldexcitation suppliig by said REFERENCES CITED arma me to sa d reversefield winding 9. value insumcient to maintain magnetization of said 2ffig ii are 0f recm'd the field in the absence of excitation supplied bysaid n independent excitation source. 5 NITED STATES PATENTS Number NameDate HENRY fag- 1,998,209 Sundhaussen Apr. 16, 1935 2,287,835 SatterleeJune 30, 1942

